General Chemistry Principles, Patterns, and Applications, 2011

2. Silver is tarnished by hydrogen sulfide, an atmospheric contaminant, to form a thin layer of dark silver sulfide
(Ag 2 S) along with hydrogen gas.
a. Write a balanced chemical equation for this reaction.
b. Which species has been oxidized and which has been reduced?
c. Assuming 2.2 g of Ag has been converted to silver sulfide, construct a table showing the reaction in terms of
the number of atoms in the reactants and products, the moles of reactants and products, the grams of
reactants and products, and the molecules of reactants and products.
13. The following reaction is used in the paper and pulp industry:
Na 2 SO 4 (aq) + C(s) + NaOH(aq) → Na 2 CO 3 (aq) + Na 2 S(aq) + H 2 O(l)
d. Balance the chemical equation.
e. Identify the oxidant and the reductant.
f. How much carbon is needed to convert 2.8 kg of sodium sulfate to sodium sulfide?
g. If the yield of the reaction were only 78%, how many kilograms of sodium carbonate would be produced
from 2.80 kg of sodium sulfate?
h. If 240 g of carbon and 2.80 kg of sodium sulfate were used in the reaction, what would be the limiting
reactant (assuming an excess of sodium hydroxide)?
14. The reaction of A 2 (blue) with B 2 (yellow) is shown below. The initial reaction mixture is shown on the left
and the mixture after the reaction has gone to completion is shown on the right.
a. Write a balanced chemical equation for the reaction.
b. Which is the limiting reactant in the initial reaction mixture?
c. How many moles of the product AB 4 could you obtain from a mixture of 0.020 mol A 2 and 0.060 mol B 2 ?
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